Genetic Silencing of AKT Induces Melanoma Cell Death via mTOR Suppression

Aberrant activation of the PI3K-AKT pathway is common in many cancers, including melanoma, and AKT1, 2 and 3 (AKT1-3) are bona fide oncoprotein kinases with well-validated downstream effectors. However, efforts to pharmacologically inhibit AKT have proven to be largely ineffective. In this study, we observed paradoxical effects following either pharmacologic or genetic inhibition of AKT1-3 in melanoma cells. Although pharmacological inhibition was without effect, genetic silencing of all three AKT paralogs significantly induced melanoma cell death through effects on mTOR. This phenotype was rescued by exogenous AKT1 expression in a kinase-dependent manner. Pharmacological inhibition of PI3K and mTOR with a novel dual inhibitor effectively suppressed melanoma cell proliferation in vitro and inhibited tumor growth in vivo. Furthermore, this single-agent-targeted therapy was well-tolerated in vivo and was effective against MAPK inhibitor-resistant patient-derived melanoma xenografts. These results suggest that inhibition of PI3K and mTOR with this novel dual inhibitor may represent a promising therapeutic strategy in this disease in both the first-line and MAPK inhibitor-resistant setting.

Abstract 427: Newer generation mTOR inhibition represents effective therapeutic strategy for BRAF-mutant melanoma

Despite the advent of novel therapies, the five year survival rate for Stage IV melanoma remains at only 30%. This highlights the critical need for new therapeutics to treat this refractory disease. Aberrant activation of the PI3K-AKT pathway is common in melanoma, but efforts to drug this pathway have proven largely ineffective in clinical trials. In our study, we observed that pharmacological inhibition of AKT was ineffective whereas genetic silencing of all three AKT paralogs significantly abrogated melanoma cell growth and led to apoptosis through effects on mTORC signaling. This phenotype could be rescued by overexpression of AKT but was dependent on kinase activity. Interestingly, expression of the serine/threonine kinase SGK1 was increased following genetic suppression of AKT but only expression of activated SGK1 could rescue the lethal effect of AKT knockdown. SGK1 also increases tumor growth and decreases survival in a BRAFV600E-driven mouse model of melanoma. Despite our results suggesting that key proliferation of melanoma cells is through effects on mTOR, phase II clinical trials of mTOR inhibitors have not shown clinical advantage. This may be due to multiple reasons: firstly, mTOR inhibitors, such as rapamycin, function by destabilization of the mTORC1-Raptor complex while leaving the mTORC2-Rictor complex, intact. Rictor enables mTORC2 to directly phosphorylate Ser473, and facilitates Thr308 phosphorylation by PDK1. As both AKT and SGK are phosphorylated by mTORC2 and PDK1 to facilitate downstream signaling through mTORC1, residual activity of mTOR incompletely suppressed by rapamycin may still be sufficient to drive melanoma progression. Thus, we evaluated second and third generation mTORC inhibitors, including a dual PI3K/mTOR inhibitor, that target both mTORC1 and 2 complexes and lead to sustained suppression of PI3K>AKT signaling. The dual PI3K/mTORC inhibitor, Paxalisib, significantly reduced cell proliferation greater than combination AKT/SGK inhibition and resulted in increased overall survival in a BRAF-driven immunocompetent mouse model of melanoma (p=0.0003 vs vehicle). These results allow insight into compensatory signaling networks upon AKT inhibition and suggest that dual targeting of PI3K and both mTOR complexes may represent an effective and tolerable therapeutic strategy in this disease that could further be combined with standard of care targeted therapy.

Citation Format: Gennie L. Parkman, Tursun Turapov, David Kircher, William Burnett, Christopher Stehn, Kayla O'Toole, Katie Culver, Ashley Chadwick, Riley Elmer, Ryan Flaherty, Mona Foth, Karly Stanley, Robert Andtbacka, David Lum, Robert Judson-Torres, Martin McMahon, Sheri Holmen. Newer generation mTOR inhibition represents effective therapeutic strategy for BRAF-mutant melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 427.

Loss of Cxcr2 in Myeloid Cells Promotes Tumour Progression and T Cell Infiltration in Invasive Bladder Cancer

BACKGROUND: CXCR2 is a chemokine receptor expressed in myeloid cells, including neutrophils and macrophages. Pharmacological inhibition of CXCR2 has been shown to sensitize tumours to immune checkpoint inhibitor immunotherapies in some cancer types. OBJECTIVE: To investigate the effects of CXCR2 loss in regulation of tumour-infiltrating myeloid cells and their relationship to lymphocytes during bladder tumorigenesis. METHODS: Urothelial pathogenesis and immune contexture was investigated in an OH-BBN model of invasive bladder cancer with Cxcr2 deleted in myeloid cells (LysMCre Cxcr2floxflox). CXCR2 gene alterations and expression in human muscle invasive bladder cancer were analysed in The Cancer Genome Atlas. RESULTS: Urothelial tumour pathogenesis was significantly increased upon Cxcr2 deletion compared to wildtype mice. This was associated with a suppression of myeloid cell infiltration in Cxcr2-deleted bladders shortly after the carcinogen induction. Interestingly, following a transient increase of macrophages at the outset of tumour formation, an increase in T cell infiltration was observed in Cxcr2-deleted tumours. The increased tumour burden in the Cxcr2-deleted bladder was largely independent of T cells and the status of immune suppression. The Cxcr2-deleted mouse model reflected the low CXCR2 mRNA range in human bladder cancer, which showed poor overall survival. CONCLUSIONS: In contrast to previous reports of increased CXCR2 signalling associated with disease progression and poor prognosis, CXCR2 was protective against bladder cancer during tumour initiation. This is likely due to a suppression of acute inflammation. The strategy for sensitizing checkpoint immunotherapy by CXCR2 inhibition in bladder cancer may benefit from an examination of immune suppressive status.

The role of PI3'-lipid signalling in melanoma initiation, progression and maintenance

Phosphatidylinositol-3'-kinases (PI3Ks) are a family of lipid kinases that phosphorylate the 3' hydroxyl (OH) of the inositol ring of phosphatidylinositides (PI). Through their downstream effectors, PI3K generated lipids (PI3K-lipids hereafter) such as PI(3,4,5)P3 and PI(3,4)P2 regulate myriad biochemical and biological processes in both normal and cancer cells including responses to growth hormones and cytokines; the cell division cycle; cell death; cellular growth; angiogenesis; membrane dynamics; and autophagy and many aspects of cellular metabolism. Engagement of receptor tyrosine kinase by their cognate ligands leads to activation of members of the Class I family of PI3'-kinases (PI3Kα, β, δ & γ) leading to accumulation of PI3K-lipids. Importantly, PI3K-lipid accumulation is antagonized by the hydrolytic action of a number of PI3K-lipid phosphatases, most notably the melanoma suppressor PTEN (lipid phosphatase and tensin homologue). Downstream of PI3K-lipid production, the protein kinases AKT1-3 are believed to be key effectors of PI3'-kinase signalling in cells. Indeed, in preclinical models, activation of the PI3K→AKT signalling axis cooperates with alterations such as expression of the BRAFV600E oncoprotein kinase to promote melanoma progression and metastasis. In this review, we describe the different classes of PI3K-lipid effectors, and how they may promote melanomagenesis, influence the tumour microenvironment, melanoma maintenance and progression to metastatic disease. We also provide an update on both FDA-approved or experimental inhibitors of the PI3K→AKT pathway that are currently being evaluated for the treatment of melanoma either in preclinical models or in clinical trials.

Therapeutic Targeting of Autophagy in Pancreatic Cancer

This article provides a brief review of the therapeutic opportunity of inhibiting autophagy in pancreatic cancer. The autophagic process, importance of autophagy in pancreatic cancer, relevant clinical trials, and new agents in preclinical and clinical development are discussed.

Abstract IA25: Targeting MEK1/2 inhibitor resistance in RAS-mutated cancers

Although the RAF>MEK>ERK MAP kinase pathway is key to the development of many RAS-mutated cancers, efforts to target this pathway with pharmacologic inhibitors have failed to deliver clinical benefit to patients. Here we show that inhibition of RAS>RAF>MEK>ERK signaling in RAS-mutated cancer cell lines elicits autophagy, a process of cellular recycling that protects cancer cells from the potentially cytotoxic effects of RAF>MEK>ERK pathway inhibition. Furthermore, combined inhibition of MEK1/2 plus autophagy displays synergistic antiproliferative effects against cell lines in vitro and promotes regression of xenografted patient-derived tumors in mice. Finally, treatment of a cancer patient with the combination of trametinib plus hydroxychloroquine resulted in a partial, but nonetheless striking, disease response. These data suggest that this combination therapy may represent a novel strategy to target RAS-driven malignancies such as melanoma, lung, and pancreatic cancer.

Citation Format: Conan Kinsey, Soledad Camolotto, Amelie Boespflug, Katrin Gullien, Amanda Truong, Mona Foth, Jill Shea, Michael Seipp, Jeffrey Yap, Lance Burrell, David Lum, Jonathan Whisenant, Courtney Cavalier, Kaitren Rehbein, Stephanie Cutler, Kajsa Afotler, Alana Welm, Bryan Welm, Courtney Scaife, Eric Snyder, Martin McMahon. Targeting MEK1/2 inhibitor resistance in RAS-mutated cancers [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr IA25.

Abstract 1225: Co-inhibition of autophagy and MAPK signaling in RAS-driven cancers

RASis mutated in a number of cancers, including KRAS-driven colorectal and pancreatic cancer, HRAS-driven bladder cancer, and NRAS-driven melanoma, all of which result in downstream activation of the RAF>MEK>ERK (MAPK) and PI3K>AKT signaling pathways. Most RAS GTPases cannot be targeted directly, and strategies blocking both MAPK and PI3K signaling simultaneously are limited by high toxicity and compensatory signaling mechanisms. Interestingly, oncogene-activated MAPK or PI3K signaling pathways are reasonably well described orchestrators of metabolic transformation through multiple pathways. Our lab has recently shown that autophagy,a conserved metabolic process of self-digestion that recycles intracellular components, is increased in KRAS-driven pancreatic ductal adenocarcinoma (PDA) upon MAPK pathway inhibition. We further showed that co-inhibition of autophagy and MEK1/2, a MAPK component, leads to tumor regression of patient-derived PDA xenografts in mice. Our proposed combination therapy has recently been translated into a phase I/II clinical trial for PDA patients with advanced disease. Our most recent data show that inhibition of RAS>RAF>MEK>ERK signaling also results in induction of autophagy in other RAS-driven cancers, including KRAS-driven colorectal cancer, HRAS-driven bladder cancer and NRAS-driven melanoma. Furthermore, ourin vivodata demonstrate a robust regression of tumors upon combined inhibition of autophagy and MEK1/2 in engrafted KRAS-driven colorectal cancer cells xenografted in mice. Patient data from two KRAS-driven colorectal cancer patients, who were recently treated off-label, indicated clinical responses to the combination treatment co-targeting autophagy and MEK1/2. Altogether, these data suggest that co-inhibition of autophagy and oncogenic signaling may represent a potential new treatment strategy for multiple RAS-driven cancer types. Future experiments aim for a better mechanistic understanding of the combination treatment co-targeting autophagy and oncogenic signaling, with the objective to propose novel therapeutic strategies for cancer patients with RASmutations.

Citation Format: Mona Foth, Conan Kinsey, Sophia Schuman, Benjamin Battistone, Emilio Cortes Sanchez, David Kircher, Bryan Welm, Sheri Holmen, Martin McMahon. Co-inhibition of autophagy and MAPK signaling in RAS-driven cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1225.

RAC1mutation is not a predictive biomarker for PI3'-kinase-β-selective pathway-targeted therapy

Mutational activation of RAC1 is detected in ~7% of cutaneous melanoma, with the most frequent mutation (RAC1^C85T ) encoding for RAC1^P29S . RAC1^P29S is a fast-cycling GTPase that leads to accumulation of RAC1^P29S -GTP, which has potentially pleiotropic regulatory functions in melanoma cell signaling and biology. However, the precise mechanism by which mutationally activated RAC1^P29S propagates its pro-tumorigenic effects remains unclear. RAC1-GTP is reported to activate the beta isoform of PI3'-kinase (PIK3CB/PI3Kβ) leading to downstream activation of PI3'-lipid signaling. Hence, we employed both genetic and isoform-selective pharmacological inhibitors to test if RAC1^P29S propagates its oncogenic signaling in melanoma through PI3Kβ. We observed that RAC1^P29S -expressing melanoma cells were largely insensitive to inhibitors of PI3Kβ. Furthermore, RAC1^P29S melanoma cell lines showed variable sensitivity to pan-class 1 (α/β/γ/δ) PI3'-kinase inhibitors, suggesting that RAC1-mutated melanoma cells may not rely on PI3'-lipid signaling for their proliferation. Lastly, we observed that RAC1^P29S -expressing cell lines also showed variable sensitivity to pharmacological inhibition of the RAC1 → PAK1 signaling pathway, questioning the relevance of inhibitors of this pathway for the treatment of patients with RAC1-mutated melanoma.

Abstract A45: Protective autophagy elicited by RAF→MEK→ERK inhibition suggests a treatment strategy for RAS-driven cancers

Pancreatic ductal adenocarcinoma was responsible for ~43,000 deaths in the USA in 2017 and is the epitome of a recalcitrant cancer driven by a pharmacologically intractable oncoprotein, KRAS. Although the clinical picture remains grim, the mechanisms by which key alterations in tumor suppressors and proto-oncogenes contribute to PDA have been dissected. Downstream of KRAS, the RAF→MEK→ERK signaling pathway plays a central role in pancreatic carcinogenesis. However, to date, pharmacologic inhibition of this pathway has provided no clinical benefit to PDA patients. Here we show that inhibition of KRAS→RAF→MEK→ERK signaling in PDA cell lines elicits autophagy, a process of cellular recycling that protects pancreatic cancer cells from the potentially cytotoxic effects of KRAS pathway inhibition. Furthermore, combined inhibition of MEK1/2 plus autophagy displays synergistic antiproliferative effects against PDA cell lines in vitro, and promotes regression of xenografted patient-derived PDA tumors in mice. Finally, treatment of a KRAS-mutated PDA patient on a compassionate basis with the combination of trametinib plus hydroxychloroquine resulted in a partial but nonetheless striking disease response. These data suggest that this combination therapy may represent a new strategy to target RAS-driven cancers such as PDA.

Citation Format: Conan G. Kinsey, Soledad A. Camolotto, Amelie M. Boespflug, Katrin P. Gullien, Mona Foth, Jill E. Shea, Michael T. Seipp, Jeffrey T. Yap, Lance D. Burrell, David H. Lum, Jonathan R. Whisenant, Weldon Gilcrease, Courtney C. Cavalieri, Kaitrin M. Rehbein, Stephanie L. Cutler, Kajsa E. Affolter, Alana L. Welm, Bryan E. Welm, Courtney L. Scaife, Eric L. Snyder, Martin McMahon. Protective autophagy elicited by RAF→MEK→ERK inhibition suggests a treatment strategy for RAS-driven cancers [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A45.

Determination of Percentage of RoundUp Ready® Soya in Soya Flour Using Real-Time Polymerase Chain Reaction: Interlaboratory Study

An interlaboratory study was conducted to evaluate a method for determination of the percentage of RoundUp Ready® (RR) soya in soya flour using Taqman® technology. The method included DNA extraction from the test portion with cetyltrimethylammonium bromide buffer followed by chloroform extraction and Wizard® resin cleanup steps. The DNA was then assayed with primer and probe sets specific for lectin as the endogenous control and the RR insert as the target. The percentage of RR soya in the soya fraction of the sample was calculated by using a matrix-matched standard curve. Ten samples of split-level blind duplicates were sent to 22 laboratories in 12 countries worldwide. Test portions contained 0, 0.5, 0.7, 1.6, 2, and 3.9% (w/w) RR soya prepared gravimetrically from commercially available RR standard reference materials. Based on the results for test materials, the relative standard deviation for repeatability (RSDr) for the method ranged from 9.3 to 19.3% and, for reproducibility (RSDR), ranged from 20.3 to 33.7%.

Ergonomics in apiculture: A case study based on inspecting movable frame hives for healthy bee activities

The agricultural sector suffers from high risk of injury and damage to human health. There is considerable research not only identifying these risks but also finding ways to mitigate them. Beekeeping or apiculture, recognised as part of this sector, has many risk factors such as heavy lifting, high degree of manual materials handling, twisting, and awkward positioning common to all agriculture areas. It also has some unique risks such as those resulting from bee stings and smokers. However, there is much less attention focused on the health and safety of apiculture to the human beekeepers, and much more attention focused on bee health and safety. An ergonomics case study on beekeeping inspection tasks involving three independent, local beekeepers showed that many tasks involve awkward positions of the body, arms and hands, excessive lifting well beyond recommended weight limits, eye strain, and chemical and sting exposure. In addition, beekeepers are more interested in bee and hive health rather than reducing human-centred risk factors such as those due to excessive lifting. Standard ergonomics interventions such as a magnifier inspection and lift assist systems as well as interventions unique to beekeeping such as a smokeless method of calming bees are recommended. The beekeeping industry seems to have been forgotten in the modernisation of technology and agricultural practices. This paper offers some initial insights into possible points for research, development and improvements.

Abstract 2183: Protective autophagy elicited by RAF®MEK®ERK inhibition suggests a treatment strategy for pancreatic cancer

Pancreatic ductal adenocarcinoma was responsible for ~43,000 deaths in the USA in 2017 and is the epitome of a recalcitrant cancer driven by an, as yet, pharmacologically intractable oncoprotein, KRAS. Although the clinical picture remains grim, the mechanisms by which key alterations in tumor suppressors and proto-oncogenes contribute to PDA have been dissected. Downstream of KRAS, the RAF→MEK→ERK signaling pathway plays a central role in pancreatic carcinogenesis. However, to date, pharmacological inhibition of this pathway has provided no clinical benefit to PDA patients. Here we show that inhibition of KRAS→RAF→MEK→ERK signaling in PDA cell lines elicits autophagy, a process of cellular recycling that protects pancreatic cancer cells from the potentially cytotoxic effects of KRAS pathway inhibition. Furthermore, combined inhibition of MEK1/2 plus autophagy displays synergistic anti-proliferative effects against PDA cell lines in vitro, and promotes regression of xenografted patient-derived PDA tumors in mice. Finally, treatment of a PDA patient with the combination of trametinib plus hydroxychloroquine resulted in a partial, but nonetheless striking disease response. These data suggest that this combination therapy may represent a novel strategy to target RAS-driven cancers such as PDA.

Citation Format: Conan G. Kinsey, Soledad A. Camolotto, Amelie M. Boespflug, Katrin P. Guillen, Mona Foth, Amanda Truong, Sophia S. Schuman, Jill E. Shea, Michael T. Seipp, Jeffrey T. Yap, Lance D. Burrell, David H. Lum, Jonathan R. Whisenant, G. Weldon Gilcrease, Courtney C. Cavalieri, Kaitrin M. Rehbein, Stephanie L. Cutler, Kajsa E. Affolter, Alana L. Welm, Bryan E. Welm, Courtney L. Scaife, Eric L. Snyder, Martin McMahon. Protective autophagy elicited by RAF®MEK®ERK inhibition suggests a treatment strategy for pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2183.

Protective autophagy elicited by RAF→MEK→ERK inhibition suggests a treatment strategy for RAS-driven cancers

Pancreatic ductal adenocarcinoma (PDA) was responsible for ~ 44,000 deaths in the United States in 2018 and is the epitome of a recalcitrant cancer driven by a pharmacologically intractable oncoprotein, KRAS1-4. Downstream of KRAS, the RAF→MEK→ERK signaling pathway plays a central role in pancreatic carcinogenesis5. However, paradoxically, inhibition of this pathway has provided no clinical benefit to patients with PDA6. Here we show that inhibition of KRAS→RAF→MEK→ERK signaling elicits autophagy, a process of cellular recycling that protects PDA cells from the cytotoxic effects of KRAS pathway inhibition. Mechanistically, inhibition of MEK1/2 leads to activation of the LKB1→AMPK→ULK1 signaling axis, a key regulator of autophagy. Furthermore, combined inhibition of MEK1/2 plus autophagy displays synergistic anti-proliferative effects against PDA cell lines in vitro and promotes regression of xenografted patient-derived PDA tumors in mice. The observed effect of combination trametinib plus chloroquine was not restricted to PDA as other tumors, including patient-derived xenografts (PDX) of NRAS-mutated melanoma and BRAF-mutated colorectal cancer displayed similar responses. Finally, treatment of a patient with PDA with the combination of trametinib plus hydroxychloroquine resulted in a partial, but nonetheless striking disease response. These data suggest that this combination therapy may represent a novel strategy to target RAS-driven cancers.

FGFR3 mutation increases bladder tumourigenesis by suppressing acute inflammation

Recent studies of muscle-invasive bladder cancer show that FGFR3 mutations are generally found in a luminal papillary tumour subtype that is characterised by better survival than other molecular subtypes. To better understand the role of FGFR3 in invasive bladder cancer, we examined the process of tumour development induced by the tobacco carcinogen OH-BBN in genetically engineered models that express mutationally activated FGFR3 S249C or FGFR3 K644E in the urothelium. Both occurrence and progression of OH-BBN-driven tumours were increased in the presence of an S249C mutation compared to wild-type control mice. Interestingly, at an early tumour initiation stage, the acute inflammatory response in OH-BBN-treated bladders was suppressed in the presence of an S249C mutation. However, at later stages of tumour progression, increased inflammation was observed in S249C tumours, long after the carcinogen administration had ceased. Early-phase neutrophil depletion using an anti-Ly6G monoclonal antibody resulted in an increased neutrophil-to-lymphocyte ratio at later stages of pathogenesis, indicative of enhanced tumour pathogenesis, which supports the hypothesis that suppression of acute inflammation could play a causative role. Statistical analyses of correlation showed that while initial bladder phenotypes in morphology and inflammation were FGFR3-dependent, increased levels of inflammation were associated with tumour progression at the later stage. This study provides a novel insight into the tumour-promoting effect of FGFR3 mutations via regulation of inflammation at the pre-tumour stage in the bladder. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Comprehensive DNA methylation study identifies novel progression-related and prognostic markers for cutaneous melanoma

BACKGROUND

Cutaneous melanoma is the deadliest skin cancer, with an increasing incidence and mortality rate. Currently, staging of patients with primary melanoma is performed using histological biomarkers such as tumor thickness and ulceration. As disruption of the epigenomic landscape is recognized as a widespread feature inherent in tumor development and progression, we aimed to identify novel biomarkers providing additional clinical information over current factors using unbiased genome-wide DNA methylation analyses.

METHODS

We performed a comprehensive DNA methylation analysis during all progression stages of melanoma using Infinium HumanMethylation450 BeadChips on a discovery cohort of benign nevi (n = 14) and malignant melanoma from both primary (n = 33) and metastatic (n = 28) sites, integrating the DNA methylome with gene expression data. We validated the discovered biomarkers in three independent validation cohorts by pyrosequencing and immunohistochemistry.

RESULTS

We identified and validated biomarkers for, and pathways involved in, melanoma development (e.g., HOXA9 DNA methylation) and tumor progression (e.g., TBC1D16 DNA methylation). In addition, we determined a prognostic signature with potential clinical applicability and validated PON3 DNA methylation and OVOL1 protein expression as biomarkers with prognostic information independent of tumor thickness and ulceration.

CONCLUSIONS

Our data underscores the importance of epigenomic regulation in triggering metastatic dissemination through the inactivation of central cancer-related pathways. Inactivation of cell-adhesion and differentiation unleashes dissemination, and subsequent activation of inflammatory and immune system programs impairs anti-tumoral defense pathways. Moreover, we identify several markers of tumor development and progression previously unrelated to melanoma, and determined a prognostic signature with potential clinical utility.

CXCR2 Inhibition Profoundly Suppresses Metastases and Augments Immunotherapy in Pancreatic Ductal Adenocarcinoma

CXCR2 has been suggested to have both tumor-promoting and tumor-suppressive properties. Here we show that CXCR2 signaling is upregulated in human pancreatic cancer, predominantly in neutrophil/myeloid-derived suppressor cells, but rarely in tumor cells. Genetic ablation or inhibition of CXCR2 abrogated metastasis, but only inhibition slowed tumorigenesis. Depletion of neutrophils/myeloid-derived suppressor cells also suppressed metastasis suggesting a key role for CXCR2 in establishing and maintaining the metastatic niche. Importantly, loss or inhibition of CXCR2 improved T cell entry, and combined inhibition of CXCR2 and PD1 in mice with established disease significantly extended survival. We show that CXCR2 signaling in the myeloid compartment can promote pancreatic tumorigenesis and is required for pancreatic cancer metastasis, making it an excellent therapeutic target.

Prognostic and predictive biomarkers in melanoma: an update

Malignant melanoma is one of the most aggressive cancers. Several new therapeutic strategies that focus on immuno- and/or targeted therapy have been developed, which have entered clinical trials or already been approved. This review provides an update on prognostic and predictive biomarkers in melanoma that may be used to improve the clinical management of patients. Prognostic markers include conventional histopathological characteristics, chromosomal aberrations, gene expression patterns and miRNA profiles. There is a trend towards multi-marker assays and whole-genome molecular screening methods to determine the prognosis of individual patients. Predictive biomarkers, including targeted components of signal transduction, developmental or transcriptional pathways, can be used to determine patient response towards a particular treatment or combination thereof. The rapid evolution of sequencing technologies and multi-marker screening will change the spectrum of patients who become candidates for therapeutic agents, and in addition create new ethical and regulatory challenges.

CXCR2 inhibition suppresses acute and chronic pancreatic inflammation

Pancreatitis is a significant clinical problem and the lack of effective therapeutic options means that treatment is often palliative rather than curative. A deeper understanding of the pathogenesis of both acute and chronic pancreatitis is necessary to develop new therapies. Pathological changes in pancreatitis are dependent on innate immune cell recruitment to the site of initial tissue damage, and on the coordination of downstream inflammatory pathways. The chemokine receptor CXCR2 drives neutrophil recruitment during inflammation, and to investigate its role in pancreatic inflammation, we induced acute and chronic pancreatitis in wild-type and Cxcr2(-/-) mice. Strikingly, Cxcr2(-/-) mice were strongly protected from tissue damage in models of acute pancreatitis, and this could be recapitulated by neutrophil depletion or by the specific deletion of Cxcr2 from myeloid cells. The pancreata of Cxcr2(-/-) mice were also substantially protected from damage during chronic pancreatitis. Neutrophil depletion was less effective in this model, suggesting that CXCR2 on non-neutrophils contributes to the development of chronic pancreatitis. Importantly, pharmacological inhibition of CXCR2 in wild-type mice replicated the protection seen in Cxcr2(-/-) mice in acute and chronic models of pancreatitis. Moreover, acute pancreatic inflammation was reversible by inhibition of CXCR2. Thus, CXCR2 is critically involved in the development of acute and chronic pancreatitis in mice, and its inhibition or loss protects against pancreatic damage. CXCR2 may therefore be a viable therapeutic target in the treatment of pancreatitis.

Fibroblast growth factor receptor 3 activation plays a causative role in urothelial cancer pathogenesis in cooperation with Pten loss in mice

Although somatic mutations and overexpression of the tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) are strongly associated with bladder cancer, evidence for their functional involvement in the pathogenesis remains elusive. Previously we showed that activation of Fgfr3 alone is not sufficient to initiate urothelial tumourigenesis in mice. Here we hypothesize that cooperating mutations are required for Fgfr3-dependent tumourigenesis in the urothelium and analyse a mouse model in which an inhibitor of Pi3k-Akt signalling, Pten, is deleted in concert with Fgfr3 activation (UroIICreFgfr3(+/) (K644E) Pten(flox) (/flox)). Two main phenotypical characteristics were observed in the urothelium: increased urothelial thickness and abnormal cellular histopathology, including vacuolization, condensed cellular appearance, enlargement of cells and nuclei, and loss of polarity. These changes were not observed when either mutation was present individually. Expression patterns of known urothelial proteins indicated the abnormal cellular differentiation. Furthermore, quantitative analysis showed that Fgfr3 and Pten mutations cooperatively caused cellular enlargement, while Pten contributed to increased cell proliferation. Finally, FGFR3 overexpression was analysed along the level of phosphorylated mTOR in 66 T1 urothelial tumours in tissue microarray, which supported the occurrence of functional association of these two signalling pathways in urothelial pathogenesis. Taken together, this study provides evidence supporting a functional role of FGFR3 in the process of pathogenesis in urothelial neoplasms. Given the wide availability of inhibitors specific to FGF signalling pathways, our model may open the avenue for FGFR3-targeted translation in urothelial disease.

A component of the mir-17-92 polycistronic oncomir promotes oncogene-dependent apoptosis

mir-17-92, a potent polycistronic oncomir, encodes six mature miRNAs with complex modes of interactions. In the Eμ-myc Burkitt’s lymphoma model, mir-17-92 exhibits potent oncogenic activity by repressing c-Myc-induced apoptosis, primarily through its miR-19 components. Surprisingly, mir-17-92 also encodes the miR-92 component that negatively regulates its oncogenic cooperation with c-Myc. This miR-92 effect is, at least in part, mediated by its direct repression of Fbw7, which promotes the proteosomal degradation of c-Myc. Thus, overexpressing miR-92 leads to aberrant c-Myc increase, imposing a strong coupling between excessive proliferation and p53-dependent apoptosis. Interestingly, miR-92 antagonizes the oncogenic miR-19 miRNAs; and such functional interaction coordinates proliferation and apoptosis during c-Myc-induced oncogenesis. This miR-19:miR-92 antagonism is disrupted in B-lymphoma cells that favor a greater increase of miR-19 over miR-92. Altogether, we suggest a new paradigm whereby the unique gene structure of a polycistronic oncomir confers an intricate balance between oncogene and tumor suppressor crosstalk.

DOI:http://dx.doi.org/10.7554/eLife.00822.001

The role of genes, in very simple terms, is to be transcribed into messenger RNA molecules, which are then translated into strings of amino acids that fold into proteins. Each of these steps is extremely complex, and a wide range of other molecules can speed up, slow down, stop or otherwise disrupt the expression of genes as protein products. Genes can also code for nucleic acids that are not translated into proteins, such as microRNAs. These are small RNA molecules that can reduce the production of proteins by repressing the translation step and/or by partially degrading the messenger RNA molecules.

mir-17-92 is a gene that exemplifies much of this complexity. It codes for six different microRNAs in a single primary transcript, and has been implicated in a number of cancers, including lung cancer, Burkitt’s lymphoma and other forms of lymphomas and leukemia. One of six microRNAs has a longer evolutionary history than the remaining five: mir-92 is found in vertebrates, chordates and invertebrates, whereas the other five are only found in vertebrates. However, it is not known how or why the mir-17-92 gene evolved to code for multiple different microRNAs.

Olive et al. have studied how these mir-17-92 microRNAs functionally interact in mice with Burkitt’s lymphoma, a form of cancer that is associated with a gene called c-Myc being over-activated. Mutations in this gene promote the proliferation of cells, and in cooperation with other genetic lesions, this ultimately leads to cancer. mir-17-92 is implicated in this cancer because it represses the process of programmed cell death (which is induced by the protein c-Myc) that the body employs to stop tumors growing.

Olive et al. found that deleting one of the six microRNAs, miR-92, increased the tendency of the mir-17-92 gene to promote Burkitt’s lymphoma. By repressing an enzyme called Fbw7, miR-92 causes high levels of c-Myc to be produced. While this leads to the uncontrolled proliferation of cells that promotes cancer, it also increases programmed cell death, at least in part, by activating the p53 pathway, a well-known tumor suppression pathway. The experiments also revealed that the action of miR-92 and that of one of the other microRNAs, miR-19, were often opposed to each other. These findings have revealed an unexpected interaction among different components within a single microRNA gene, which acts to maintain an intricate balance between pathways that promote and suppress cancer.

DOI:http://dx.doi.org/10.7554/eLife.00822.002

K-Ras and β-catenin mutations cooperate with Fgfr3 mutations in mice to promote tumorigenesis in the skin and lung, but not in the bladder

The human fibroblast growth factor receptor 3 (FGFR3) gene is frequently mutated in superficial urothelial cell carcinoma (UCC). To test the functional significance of FGFR3 activating mutations as a 'driver' of UCC, we targeted the expression of mutated Fgfr3 to the murine urothelium using Cre-loxP recombination driven by the uroplakin II promoter. The introduction of the Fgfr3 mutations resulted in no obvious effect on tumorigenesis up to 18 months of age. Furthermore, even when the Fgfr3 mutations were introduced together with K-Ras or β-catenin (Ctnnb1) activating mutations, no urothelial dysplasia or UCC was observed. Interestingly, however, owing to a sporadic ectopic Cre recombinase expression in the skin and lung of these mice, Fgfr3 mutation caused papilloma and promoted lung tumorigenesis in cooperation with K-Ras and β-catenin activation, respectively. These results indicate that activation of FGFR3 can cooperate with other mutations to drive tumorigenesis in a context-dependent manner, and support the hypothesis that activation of FGFR3 signaling contributes to human cancer.